The present invention relates to an implantable prosthesis adapted to be inserted into a human body. More particularly, the invention relates to a prosthesis adapted to replace the junction between a pelvis and femur, i.e. a hip joint, including both the femoral portion and the acetabular cup.
Hip joint prostheses comprising a femoral stem and a cooperating acetabular cup have been in use for many years. The success rate of such implants continues to grow with increasing implant experience and the advent of new prosthesis materials, however one problem remains extant that has not abated with maturity of the procedure. The residual problem is that of the patient dislocating the hip prosthesis as a result of flexion, adduction and internal rotation of the hip joint which exceeds the ability of the components of the apparatus to remain in their intended relationship, that is for the ball, or head, to remain within the confines of the socket, or acetabular cup.
It is therefore the primary object of the present invention to provide a hip prosthesis which will accommodate substantially greater degrees of flexion, adduction and internal rotation than prior art prostheses without dislocating, that is, without the femoral head being dislodged from the cavity of the acetabular cup.
Another object of the invention is to remedy the dislocation tendency of prior hip prosthesis, and at the same time provide the patient the freedom to squat or abduct the prosthetic leg, that is, to provide for greater leg flexion, abduction and internal rotation than similar prostheses of the prior art, while at the same time allowing normal extension and abduction of the hip joint.